Analog input digital boundary scan cell, comparator, and analog switches

ABSTRACT

The disclosure describes a novel method and apparatus for improving interposers that connected stacked die assemblies to system substrates. The improvement includes the addition of IEEE 1149.1 circuitry within interposers to allow simplifying interconnect testing of digital and analog signal connections between the interposer and system substrate it is attached too. The improvement also includes the additional 1149.1 controlled circuitry that allows real time monitoring of voltage supply and ground buses in the interposer. The improvement also includes the additional of 1149.1 controlled circuitry that allows real time monitoring of functional digital and analog input and output signals in the interposer. The improvement also provides the ability to selectively serially link the 1149.1 circuitry in the interposer with 1149.1 circuitry in the die of the stack.

This application is a divisional of prior application Ser. No.15/227,536, filed Aug. 3, 2016, now U.S. Pat. No. 9,746,517, issued Aug.29, 2017;

This application is a divisional of prior application Ser. No.15/227,536, filed Aug. 3, 2016, currently pending;

Which was a divisional of prior application Ser. No. 14/612,748, filedFeb. 3, 2015, now U.S. Pat. No. 9,435,859, issued Sep. 6, 2016;

Which was a divisional of prior application Ser. No. 14/023,041, filedSep. 10, 2013, now U.S. Pat. No. 8,984,359, issued Mar. 17, 2015;

Which was a divisional of prior application Ser. No. 13/362,717, filedJan. 31, 2012, now U.S. Pat. No. 8,615,694, issued Dec. 24, 2013;

Which claims priority from Provisional Application No. 61/440,125, filedFeb. 7, 2011.

FIELD OF THE DISCLOSURE

This disclosure relates generally to IEEE standard 1149.1 and inparticular to the implementation of IEEE standard 1149.1 withininterposers.

BACKGROUND OF THE DISCLOSURE

Integrated circuits (ICs) may be designed to include or not include IEEE1149.1 boundary scan circuitry and interface. The benefits of including1149.1 in an IC include but are not limited to; (1) boundary scantesting of interconnects between ICs on a substrate, (2) testing of theIC, (3) debugging circuits within the IC and (4) programming circuitswithin the IC. The drawbacks of including 1149.1 in an IC include; (1)the requirement of a dedicated 4 pin test interface which increases theIC package size and a timing penalty on the ICs inputs and outputs dueto the boundary scan cell multiplexers. Most large digital ICs, such asCPUs, DSPs and ASICs, include 1149.1 for boundary scan testing and evenmore importantly to enable debug, trace and emulation of embedded corecircuits within the ICs. However, 1149.1 is not widely used in memory,analog and mixed signal ICs due to the above mentioned increase inpackage size and decrease in input and output performance. Memories inparticular are resistant to using 1149.1 due to JDEC's memory pin outstandardization.

FIG. 1 illustrates an example integrated circuit die 102 that includes afunctional circuit 104 that has external functional inputs (FIN) 106 andexternal functional outputs (FOUT) 108. Circuit 104 may havebidirectional signals as well, but for simplicity only inputs andoutputs are discussed in this disclosure. The circuit 104 may be adigital, analog or mixed signal circuit that performs the functionaloperation of the die. Circuit 104 may also be a memory circuit, such asbut not limited to a double data rate random access memory. As can beseen the die of FIG. 1 does not include 1149.1 boundary scan circuitry.

FIG. 2 illustrates an example integrated circuit die that includes afunctional circuit 104 and 1149.1 circuitry consisting of a test accessport (TAP) 204 and associated boundary register (BREG) 206. The TAP hasan external interface of TDI, TCK, TMS inputs 212 and a TDO output 214signals. The TAP responds to the TCK and TMS signals to input data fromTDI and output data to TDO. If the boundary register is selected foraccess it will shift data from TDI to TDO. During normal operation ofthe die, the boundary register couples the FIN signals 106 to theinternal inputs 208 of the circuit and the internal outputs 210 of thecircuit to the FOUT signals 108. During boundary scan test mode usingthe well known 1149.1 Extest instruction, the boundary register isolatesthe FIN signals 106 from the internal inputs 208 and the internaloutputs 210 from the FOUT signals 108. In the boundary scan test modethe boundary register can be operated to capture test data from the FINsignals 106 and update test data to the FOUT signals 108. The boundaryscan test mode enables the testing of the FIN and FOUT connectionsbetween multiple die/ICs on a substrate.

FIG. 3 illustrates the TAP 204 of die 202 in more detail. The FINsignals 106 and the 1149.1 input signals 212 define the inputs 318 tothe die. The FOUT signals 108 and the 1149.1 output signal 214 definethe outputs 320 of the die. The 1149.1 TAP includes, at minimum, a TAPstate machine (TSM) 304, an instruction register 306, a Bypass Register308, the Boundary Register 206 and TDO output multiplexers 310 and 312.While not shown, the TAP may also include other data register betweenTDI and TDO, including an optional Identification Register whichcontains a 32 bit code identifying the die. During functional operation,the FIN signals 106 and FOUT outputs signals 108 are coupled to thecircuit 104 via the boundary register 206 and buses 208 and 210. The TSM304 operates according to the well known 16 state transition diagram ofFIG. 3A in response to the TCK and TMS input signals to; (1) place theTAP is a Test Logic Reset state, (2) place the TAP in a Run Test/Idlestate, (3) perform a scan operation to the instruction register from TDIto TDO, (4) to perform a data scan operation to the Bypass Register 308from TDI to TDO or (4) perform a data scan operation to the BoundaryRegister 206 from TDI to TDO. The 1149.1 input interface 212 may includean optional TRST input, shown in dotted line, to reset the TSM and otherTAP circuits. If the TRST input is not included, a Power Up Reset (POR)circuit 316 may be used to reset the TSM and other TAP circuits.

During instruction scan operations, the TSM outputs control (CTL)signals to the instruction register 306 and multiplexer 312. In responseto the CTL signals the instruction register performs capture, shift andupdate operations. During the shift operation the instruction registershifts data from TDI to TDO via multiplexer 312.

During data scan operations, the TSM outputs CTL signals to the selecteddata register 308 or 206 and multiplexer 312. The instruction registeroutput (IRO) bus enables the selected data register and controlsmultiplexer 310 to couple the TDO output of the selected data registerto the TDO output of the die via multiplexer 312. In response to the CTLsignals the selected data register performs capture, shift and updateoperations, except for the Bypass Register 308 which does not haveupdate circuitry. During the shift operation the selected data registershifts data from TDI to TDO via multiplexers 310 and 312.

During manufacturing test of die 202, the inputs 318 and outputs 320 areconnected to a tester. The tester operates the inputs 318 and outputs320 to test the circuit 104 within the die 202. The test may includeoperating only the FIN 106 and FOUT 108 signals, operating the FIN 106,FOUT 108 and 1149.1 input 212 output 214 signals, or operating only the1149.1 input 212 and output 214 signals. After testing and found to begood, the die is ready for use within in a system.

FIG. 4 illustrates three die 402-406 connected to a system substrate 408via their inputs 318 and outputs 320. The system of this and followingexamples could be any type of electronic system such as a computersystem or a cell phone system. Each die contains a functional circuit104 and a TAP 204 as shown in FIGS. 2 and 3. The functional circuits 104of each die provide a different functional operation on the substrate.

FIG. 5 illustrates the circuits 104 of die 402-406 connected on thesystem substrate 408. The substrate provides a functional bussing path502 that connects the FIN 106 and FOUT 108 signals of the die togetherto enable the die to communicate. The substrate has FIN signals 504 toallow it to input signals from an external device, such as a keyboard,and FOUT signals 506 to allow it to output signals to an externaldevice, such as a display.

FIG. 6 illustrates the TAPs 204 of die 402-406 connected on the systemsubstrate 408. The substrate provides a serial bussing path 602 thatconnects the TAPs 204 to externally accessible 1149.1 input 212 and1149.1 output 214 signals. When an 1149.1 controller is connected to theexternal 1149.1 input and output signals, the TAPs can be seriallyaccessed to perform test or other operations. One of the most importanttest operations the TAPs perform is the verification that the FIN 106and FOUT 108 of each die are properly connected together via thesubstrate bussing path 502. This test operation is performed by loadingExtest instructions into each TAP's instruction register then operatingthe boundary registers of each TAP to test the connectivity between eachdie's FIN 106 and FOUT 108 signals.

FIG. 7 illustrates a device 700 comprising three stacked die 702-706mounted on a silicon interposer 708. Each die includes a circuit 104 anda TAP 204 as described in FIGS. 2 and 3. Again, each die circuit 104will typically provide a different functional operation. Die 702 and 704in this example are designed using through silicon vias (TSV) 710. TSVsare connectivity paths formed between the top and bottom surfaces of thedie. TSVs allow input 318 and output 320 signals to flow vertically upand down the die stack. In addition to TSV input and output signalconnections from the interposer, the die 702-704 are also connectedtogether locally using input 712 and output 714 signal connections.Interposers 708 are used to provide electrical connections between onesurface and another surface. The primary purpose of an interposer is tospread connections from fine pitch contact points on one surface towider pitch contact points on another surface. In this example, the finepitch contact points on the bottom surface of die 702 are spread tomatch the wider pitch contacts points of a system substrate device 700will be mounted on. Once the device 700 is mounted on a substrate, itreceives input signals 318 from the substrate and sources output signals320 to the substrate.

Before device 700 is assembled, each die 702-704 and the interposer 708are tested to insure the device is assembled with known good die andinterposer. As mentioned in regard to FIG. 3 the test may performed by atester operating some are all of the FIN 106 and FOUT 108 signals ofbuses 318 and 320, operating some are all of the FIN 106, FOUT 108, andthe 1149.1 input 212 output 214 signals of buses 318 and 320, oroperating only the 1149.1 input 212 and output 214 signals of buses 318and 320.

FIG. 8 illustrate a first example arrangement of how the TAPs 204 of die702-706 in device 700 may be accessed by a tester. In this example,interposer signal bussing path 802 provides the TDI and TCK inputs toall TAPs, interposer signal path 804 provides a TMS1 input to the TAP ofdie 702, interposer signal path 806 provides a TMS2 input to the TAP ofdie 704, interposer signal path 808 provides a TMS3 input to the TAP ofdie 706 and interposer signal path 810 provides the TDO outputs from allthe TAPs. Having unique TMS1-3 inputs for each TAP allows enabling oneTAP while the other TAPs are disabled. When disabled a TAP's TDO outputis tri-stated to avoid contention on signal path 1206 with an enabledTAP's TDO output. This is commonly referred to as the 1149.1 Star modeof accessing TAPs. To access the TAP of die 702 for a test or otheroperation, the tester inputs TMS1, TDI and TCK signals to the TAP viabusses 804 and 802, and receives TDO signals from the TAP via bus 810.To access the TAP of die 704 for a test or other operation, the testerinputs TMS2, TDI and TCK signals to the TAP via busses 806 and 802, andreceives TDO signals from the TAP via bus 810. To access the TAP of die706 for a test or other operation, the tester inputs TMS3, TDI and TCKsignals to the TAP via busses 808 and 802, and receives TDO signals fromthe TAP via bus 810.

FIG. 9 illustrates three devices 902-906 connected to a system substrate908 via their inputs 318 and outputs 320. Each device contains a stackof die 910 with TAPs and an interposer 708 as shown in FIGS. 7 and 8.

FIG. 10 illustrates the substrate providing a functional bussing path1002 that connects the FIN 106 and FOUT 108 signals of the devices902-906 together to enable them to communicate. The substrate has FINsignals 1004 to allow it to input signals from an external device, suchas a keyboard, and FOUT signals 1006 to allow it to output signals to anexternal device, such as a display.

FIG. 11 illustrates the substrate providing an externally accessible1149.1 signal bussing path 1102 to the TAPs of the devices 902-906.Assuming the devices are assembled as shown in FIG. 8, the 1149.1bussing path 1102 would include 9 unique TMS signals. In this example,TMS signals 1-3 would be used to individually access one of the threeTAPs of device 902, TMS signals 4-6 would be used to individually accessone of the three TAPs of device 904 and TMS signals 7-9 would be used toindividually access one of the three TAPs of device 906.

When an 1149.1 controller is connected to the externally accessible1149.1 bussing path 1102, a selected TAP in device 902 is enabled by oneof the TMS1-3 inputs, a selected TAP in device 904 is enabled by one ofthe TMS4-6 inputs and a selected TAP in device 906 is enabled by one ofthe TMST-9 inputs so that they can be serially accessed from theexternal 1149.1 input bus 212 and 1149.1 output bus. After accessingthis first group of serially connected device TAPs, the 1149.1controller can select a second group of serially connected device TAPsfor access using a different set of TMS signals, and so on. Accessingseparate groups of device TAPs can be used for performing an 1149.1Extest operation to verify that the FIN 106 and FOUT 108 signals of eachdevice are properly connected together via the substrate bussing path1002.

A first problem with the 1149.1 access approach of FIG. 11 is that the1149.1 bus 1102 requires a large number of TMS signals that must berouted through the substrate and connected to the multiple TAPs ofdevices 902-906.

A second problem with the 1149.1 access approach of FIG. 11 is thatstandard 1149.1 controllers typically only provide a single TMS signalto support 1149.1 access approaches as shown in FIG. 6. 1149.1 accessapproaches like that shown in FIG. 11 would require modifying standard1149.1 controllers to include and operate multiple TMS signals.

A third problem with the 1149.1 access approach of FIG. 11 is thatExtest operations are encumbered by having to individually selectdifferent groups of device TAPs to access their boundary register totest the FIN 106 and FOUT 108 connections to the functional bus 1002 ofthe substrate 908.

A fourth problem is that Extest operations are lengthened due to havingto shift test data through boundary register cells of the local inputs712 and outputs 714 of each die in the device. For example, when theboundary register of the TAP of die 704 of FIG. 8 is being accessedduring an Extest operation to test the die's FIN 106 and FOUT 108connections to a substrate, the boundary register cells on the die'slocal inputs 712 and outputs 714 also have to be shifted which adds tothe test time. Since the local inputs 712 and outputs 714 of each diewere tested after the device was assembled, as mentioned in regard toFIG. 7, they do not need to be tested again when the device is mountedon the substrate. Only the device's FIN 106 and FOUT 108 connections tothe substrate need to be tested.

FIG. 12 illustrate a second example arrangement of how the TAPs 204 ofdie 702-706 in device 700 may be accessed by a tester. In this example,interposer signal bussing path 1202 provides the TCK and TMS inputs toall TAPs, interposer signal path 1204 provides a TDI input to the TAP ofdie 702, a local signal path 1208 provides the TDO output of the TAP ofdie 702 to the TDI input of the TAP of die 704, a local signal path 1210provides the TDO output of the TAP of die 704 to the TDI input of theTAP of die 706 and interposer signal path 1206 provides a TDO outputfrom the TAP of die 706. In this arrangement all the die TAPs of adevice are connected in a daisy-chain and can be serially accessedtogether by the tester.

FIG. 13 illustrates three devices 1302-1306 connected to a systemsubstrate 1308 via their inputs 318 and outputs 320. Each devicecontains a stack of die 1310 with TAPs and an interposer 708 as shown inFIG. 12.

FIG. 14 illustrates the substrate providing a functional bussing path1402 that connects the FIN 106 and FOUT 108 signals of the devices1302-1306 together to enable them to communicate. The substrate has FINsignals 1404 to allow it to input signals from an external device, suchas a keyboard, and FOUT signals 1406 to allow it to output signals to anexternal device, such as a display.

FIG. 15 illustrates the substrate providing an externally accessible1149.1 signal bussing path 1502 to the TAPs of the devices 1302-1306.Assuming the devices are assembled as shown in FIG. 12, the 1149.1bussing path 1102 would provide a serial path through all the deviceTAPs using a single TMS signal. Signal path 1504 in each device isprovided to indicate the daisy-chaining of the device TAPs.

When an 1149.1 controller is connected to the externally accessible1149.1 bussing path 1502, all TAPs in devices 1302-1306 can be seriallyaccessed from the external 1149.1 input 212 to the external 1149.1output 214.

A first problem with the 1149.1 access approach of FIG. 15 is that theIEEE 1149.1 standard has rules that support only one TAP in a device tobe implemented in a system. For example a device should only have oneTAP instruction register 306, one TAP bypass register 308, one optionalTAP identification register and one TAP boundary register 206. As seenin FIG. 15, the system devices 1302-1306 each have multiple TAPinstruction registers 306, multiple TAP bypass registers 308, multipleTAP boundary registers 206 and multiple optional TAP identificationregisters. Therefore the system devices 1302-1306 of FIG. 15 areconsidered to be non-compliant with the IEEE 1149.1 standard.

A second problem is that Extest operations are lengthened due to havingto shift test data through boundary register cells of the local inputs712 and outputs 714 of the die within each device. For example, when theboundary registers of the TAPs of the device of FIG. 12 are beingaccessed during an Extest operation to test the device's FIN 106 andFOUT 108 connections to the substrate of FIG. 15, the boundary registercells on the die's local inputs 712 and outputs 714 also have to beshifted which adds to the test time. Since the local inputs 712 andoutputs 714 of each die were tested after the device was assembled, asmentioned in regard to FIG. 7, they do not need to be tested again whenthe device is mounted on the substrate. Only the device's FIN 106 andFOUT 108 connections to the substrate need to be tested.

The following disclosure provides a solution to the above mentionedproblems of FIGS. 11 and 15. The solution is based on the concept ofimproving conventional interposers to include IEEE 1149.1 TAP circuitry.

BRIEF SUMMARY OF THE DISCLOSURE

This disclosure describes an interposer that is improved to include IEEE1149.1 TAP circuitry. This 1149.1 equipped interposer can be substitutedin stacked die application in place of conventional interposers toeliminate the problems identified in regard to FIGS. 11 and 15.Additional interposer improvements are also provided and described.

BRIEF DESCRIPTION OF THE VIEWS OF THE DRAWINGS

FIG. 1 illustrates an IC.

FIG. 2 illustrates an IC with 1149.1 TAP circuitry.

FIG. 3 illustrates a more detail view of the TAP circuitry of FIG. 2.

FIG. 3A illustrates the TAP state diagram.

FIG. 4 illustrate devices on a substrate.

FIG. 5 illustrates the device functional I/O substrate connections.

FIG. 6 illustrates the device test I/O substrate connections

FIG. 7 illustrates an interposer and stacked die arrangement using TSVs.

FIG. 8 illustrates TAP test input and output interposer connectionsusing multiple TMS signals.

FIGS. 9-11 illustrate the functional and test substrate connectionsusing multiple TMS signals.

FIG. 12 illustrates TAP test input and output interposer connectionsusing a single TMS signal.

FIGS. 13-15 illustrate the functional and test substrate connectionsusing single TMS signal.

FIG. 16 illustrates an interposer and die stack according thedisclosure.

FIG. 17 illustrates a detail view of the interposer and die stackaccording the disclosure.

FIG. 18 illustrates a digital input boundary scan cell that can be usedin the interposer according to the disclosure.

FIG. 19 illustrates a digital output boundary scan cell that can be usedin the interposer according to the disclosure.

FIG. 20 illustrates a capture, shift and update scan cell that can beused in the interposer according to the disclosure.

FIG. 21 illustrates an analog input boundary scan cell that can be usedin the interposer according to the disclosure.

FIG. 22 illustrates analog output boundary scan cell that can be used inthe interposer according to the disclosure.

FIGS. 23A-23F illustrate various voltage divider circuits withamplifiers that can be used in the interposer according to thedisclosure.

FIG. 24 illustrates DAC controlled by a register connected to a TAP thatcan be used in the interposer according to the disclosure.

FIG. 25 illustrates a scan cell for building the DAC register of FIG. 24that can be used in the interposer according to the disclosure.

FIG. 26 illustrate a first multiple DAC arrangement that can be used inthe interposer according to the disclosure.

FIG. 27 illustrates a second multiple DAC arrangement that can be usedin the interposer according to the disclosure.

FIG. 28 illustrates a switch controlled by a register connected to a TAPthat can be used in the interposer according to the disclosure.

FIGS. 29-31 illustrate the functional and test substrate connectionsusing the interposer of the present disclosure.

FIG. 32 illustrates an observe only digital boundary scan cell that canbe used in the interposer according to the disclosure.

FIG. 33 illustrates detail of the scan cell of FIG. 32.

FIG. 34 illustrates an observe only analog boundary scan cell that canbe used in the interposer according to the disclosure.

FIG. 35 illustrates a bidirectional digital boundary scan cell that canbe used in the interposer according to the disclosure.

FIG. 36 illustrates a bidirectional analog boundary scan cell that canbe used in the interposer according to the disclosure.

FIG. 37 illustrates a tristate digital boundary scan cell that can beused in the interposer according to the disclosure.

FIG. 38 illustrates a tristate analog boundary scan cell that can beused in the interposer according to the disclosure.

FIG. 39 illustrates voltage, ground and signal connections in aninterposer.

FIG. 40 illustrates an interposer augmented with a TAP controlled switchto monitor/measure the signal connections of FIG. 39 according to thedisclosure.

FIG. 41 illustrates an arrangement of the interposers of FIG. 40 on asystem substrate according to the disclosure.

FIG. 42 illustrates a switch of FIG. 40 capable of differential signalmonitoring/measurement according to the disclosure.

FIG. 43 illustrates a switch of FIG. 40 capable of single ended signalmonitoring/measurement according to the disclosure.

FIG. 44 illustrates an interposer and first and second die eachincluding a TAP according to the disclosure.

FIG. 45 illustrates a apparatus for selectively connecting ordisconnecting the interposer to or from the die TAPs of FIG. 44according to the disclosure.

FIG. 45A illustrates two stacked die, one with a TAP and the otherwithout a TAP, connected to an interposer according to the disclosure.

FIG. 46 illustrates circuit for gating TCK on and off according to thedisclosure.

FIG. 47 illustrates the timing of gating TCK on, accessing die TAP(s)then gating TCK off according to the disclosure.

FIG. 48 illustrates the timing of gating TCK on, then moving theinterposer and die TAPs to the Test Logic Reset state according to thedisclosure.

FIG. 49 illustrates the interposer TAP connected in series with die TAPsto enable boundary scan testing.

FIG. 50 illustrates the interposer TAP connected in series with die TAPsto provide access to die resident debug circuitry.

FIG. 51 illustrates the interposer TAP connected in series with die TAPsto provide access to die resident trace circuitry.

FIG. 52 illustrates the interposer TAP connected in series with die TAPsto provide access to die resident instrumentation circuitry.

FIG. 53 illustrates stacked die wire bonded to the interposer of thedisclosure.

FIG. 54 illustrates multiple single or stacked die devices mounted tothe interposer of the disclosure.

FIGS. 55A-55E illustrate different scan path arrangements through theinterposer of the disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

FIG. 16 illustrates a device 1602 comprising stacked die 1604 and aninterposer 1606, the interposer including an 1149.1 TAP 204. The die inthe stack may or may not include an 1149.1 TAP, i.e. the die may be theFIG. 1 die 102, the FIG. 2 die 202 or a mixture of the FIG. 1 and FIG. 2die. The 1149.1 interposer has external inputs for receiving 1149.1input signals 212 and FIN signals 106 from a substrate 1608. The 1149.1interposer has external outputs for outputting FOUT signals 108 and an1149.1 output signal 214 to substrate 1608. The 1149.1 interposeroutputs FIN signals 1610 to the stacked die 1604 and inputs FOUT signals1612 from the stacked die 1604.

FIG. 17 illustrates the 1149.1 interposer 1606 of device 1602 in moredetail. As seen the interposer includes a TAP 204 and boundary register206 and an optional POR circuit 316. The boundary register 206 iscomposed of a series of boundary scan cells 1614 located between the TDIinput and TDO output of the boundary register. The boundary register 206receives CTL input from TAP 204 and is shown outside the TAP 204, asopposed to the view of TAP 204 in FIG. 3, to simplify the description ofFIG. 17. The TAP 204 and boundary register 206 operate as described inregard to FIG. 3.

During functional operation, i.e. when the 1149.1 Bypass, Sample orIDcode instruction is loaded into the TAP's instruction register 306,the TAP's boundary register couples FIN signals 106 to FIN signals 1610and FOUT signals 1612 to FOUT signals 108 via the boundary scan cells1614.

During Extest operation, i.e. when the Extest instruction is loaded intothe TAP's instruction register 306, the TAP's boundary registerdecouples FIN signals 106 from FIN signals 1610 and FOUT signals 1612from FOUT signals 108 via the boundary scan cells 1614. While Extest isthe current instruction, the TAP's boundary register can shift in andupdate test stimulus data on the FIN signals 1610 to the stacked die1604 and on the FOUT signals 108 to the substrate 1608. Also duringExtest operation, the TAP's boundary register can capture and shift outtest response data from the FIN signals 106 from the substrate 1608 andFOUT signals 1612 from the stacked die 1604. The FIN and FOUT signalscan be either digital signals or analog signals. Digital boundary scancells 1614 are used on digital signals and analog boundary scan cells1614 are used on analog signals.

FIG. 18 illustrates a conventional example digital input boundary scancell 1802 that can be used in the interposer's boundary register 206.The cell comprises a capture, shift and update (CSU) cell 1806 and amultiplexer 1804. The CSU cell inputs the TDI signal and the CTL signalsfrom the TAP's TSM 304 of FIG. 3 and outputs a TDO signal and an output(OUT) signal to the multiplexer. The multiplexer inputs the OUT signalfrom the CSU cell, a digital input signal from the substrate, a Modesignal from the IRO of the TAP's instruction register 306 of FIG. 3, andoutputs a digital input signal to the stacked die via a buffer 1808. Ifthe multiplexer has sufficient drive for the input to the die stack, thebuffer may be omitted.

During functional mode, the Mode signal is set to cause the multiplexerto pass the digital input signal from the substrate to the digital inputsignal of the die stack via the buffer. During Extest mode, the Modesignal is set to pass the OUT signal from the CSU cell to the digitalinput signal of the die stack via the buffer.

In either the functional or Extest mode, the CSU cell can be operated bythe TAP to capture the digital input from the substrate and shift it outon TDO. The functional mode capture and shift operation is enabled whenthe IEEE 1149.1 “Sample” instruction is loaded into the TAP instructionregister 306. The Extest mode capture and shift operation is enabledwhen the IEEE 1149.1 “Extest” instruction is loaded into the TAPinstruction register 306.

FIG. 19 illustrates a conventional digital output boundary scan cell1902 comprising a CSU cell 1806 and multiplexer 1804. The structure andoperation of the digital output boundary scan cell is identical to thedigital input boundary scan cell of FIG. 18. The only differences are;(1) it inputs a digital input from the die stack instead of from thesubstrate and outputs a digital output to the substrate instead of thedie stack and (2) it requires an output buffer 1904 on the output of themultiplexer since it must drive all the digital inputs of the devices itconnects to on the substrate's functional bus.

FIG. 20 illustrates a known example implementation of the CSU cell 1806of FIGS. 18 and 19. The CSU cell 1806 consists of a multiplexer (M)2002, a capture and shift (CS) memory 2004, and an update memory (U)2006, all connected as shown. During the capture operation, the CSmemory 2004 is controlled by the CTL inputs from the TSM 304 of TAP 204of FIG. 3 to capture data on the IN input of multiplexer 2002. Duringthe shift operation, the CS memory 2004 is controlled by the CTL inputsfrom the TSM 304 of TAP 204 of FIG. 3 to shift data from the TDI inputof multiplexer 2002 to the TDO output of the CS memory 2004. During theupdate operation, the update (U) memory 2006 is controlled by the CTLinputs from the TSM 304 of TAP 204 to update data from the CS memory2004 to the OUT output of update memory (U) 2006. During each captureshift and update scan operation, data may be updated to the update (U)memory to change the logical output state of multiplexer 1804 or tomaintain the logical output state of multiplexer 1804.

FIG. 21 illustrates an example analog input boundary scan cell 2102 ofthe present disclosure comprising a CSU cell 1806, comparator 2104 andanalog switches 2106 and 2108 that could be used on analog input signalsthat pass through the interposer. The CSU inputs the TDI signal, the CTLsignals from the TAP's TSM 304, a digital input (IN) from comparator2104, and outputs the OUT signal to switch 2106 and the TDO signal. Thecomparator 2104 inputs an analog voltage signal, such as but not limitedtoo, a sinusoidal signal or other time varying type of analog signal,from the substrate and a voltage reference (VR) level. Switch 2106inputs the OUT signal from the CSU, a voltage low (VL) drive level, avoltage high (VH) drive level, and outputs a VL or VH level to switch2108. Switch 2108 inputs the analog voltage signal from the substrate,the VH or VL drive level from switch 2106, the Mode signal from the IROof the TAP's instruction register 306, and outputs a analog voltagesignal to a unity gain voltage follower amplifier (A) 2110. Amplifier2110 inputs the analog voltage signal from switch 2108, amplifies thedrive strength of the analog voltage signal and outputs the amplifiedvoltage signal to the die stack. The CSU cell 1806 operates as describedin FIG. 18.

During functional mode, the Mode signal is set to cause switch 2108 topass the analog voltage signal from the substrate to an analog voltagesignal input of the die stack, via amplifier 2110.

During Extest mode, the Mode signal is set to cause switch 2108 to passthe VL or VH drive level from switch 2106 to the analog voltage signalinput of the die stack, via amplifier 2110. The logic state of the OUTsignal from the CSU cell 1806 determines whether switch 2106 outputs aVL or VH drive level to switch 2108. For example if OUT is low, a VLdrive level may be output and if OUT is high, a VH drive level may beoutput. The logic level of the OUT signal from the CSU cell is updatedduring TAP controlled capture, shift and update scan operations. The OUTsignal can be updated to cause switch 2106 to output a constant VL or VHsignal to switch 2108 or to output alternating VL and VH signals toswitch 2108.

In either the functional or Extest mode, the CSU cell can be operated bythe TAP to capture a digitized version of the analog voltage input fromthe substrate, via the IN output from the comparator 2104, and shift itout on TDO. The VR level to the comparator is set to output a logic highon the IN input of the CSU cell when the analog voltage input from thesubstrate is above the VR level and to output a logic low on the INinput when the analog voltage input from the substrate is below the VRlevel. The functional mode capture and shift operation is enabled whenthe IEEE 1149.1 “Sample” instruction is loaded into the TAP instructionregister 306. The Extest mode capture and shift operation is enabledwhen the IEEE 1149.1 “Extest” instruction is loaded into the TAPinstruction register 306.

FIG. 22 illustrates an example analog output boundary scan cell 2202 ofthe present disclosure comprising a CSU cell 1806, comparator 2104 andanalog switches 2106 and 2108 that could be used on analog outputsignals that pass through the interposer. A unity gain voltage followeramplifier (A) 2204 is placed on the output of switch 2108 to amplify thedrive strength of the analog voltage signal input to the substrate. Thestructure and operation of the analog output boundary scan cell isidentical to the analog input boundary scan cell of FIG. 21. The onlydifferences are; (1) it inputs an analog voltage signal from the diestack instead of from the substrate and outputs an analog voltage signalto the substrate instead of the die stack and (2) the output drive ofthe amplifier 2204 is greater than the output drive of the amplifier2110 of FIG. 21 since it must drive all the analog inputs of the devicesit connects to on the substrate.

Analog circuits in devices that communicate together via the analogboundary cells of the interposer's boundary register may communicateusing different voltage ranges. For example, a first group of analogcircuits may communicate through the cells using a voltage range ofground to +3 volts, a second group of analog circuits may communicatethrough the cells using a voltage range of ground to −3 volts, and athird group of analog circuits may communicate through the cells using avoltage range of −5 to +5 volts. If the supplies (+3, −3, +5 and −5) forthese voltage ranges pass through the interposer, they can be tapped toprovide the appropriate VL and VH drive levels for an associated groupof analog boundary scan cells. A mid point voltage can be tapped, via avoltage divider between ground and +3V, to provide the VR for digitizingcomparators 2104 in analog boundary scan cells on signal paths operatingfrom ground to +3V. A mid point voltage can be tapped, via a voltagedivider between ground and −3V, to provide the VR for digitizingcomparators 2104 in analog boundary scan cells on signal paths operatingfrom ground to −3V. Ground can be tapped to provide the VR fordigitizing comparators 2105 in analog boundary scan cells on signalpaths operating from −5V to +5V.

If the required voltage supplies above do not pass through theinterposer, for example if only +10 and −10 supply voltage pass throughthe interposer, the lower level voltages −3, +3, −5, +5 and theassociated VR's must be provided by circuitry in the interposer. Thiswould be the case when die in the stack receive higher level voltages(i.e. the +10 and −10 supplies) and internally provide the lower levelvoltages using embedded voltage regulator circuits.

FIGS. 23A-23F illustrates voltage divider circuits that can beimplemented in the interposer to provide the required voltages for theabove mentioned first, second and third groups of analog boundary scancells. Each circuit includes an appropriate resistive voltage dividerand a voltage follower amplifier (A). FIG. 23A provides the +3V VHlevel, FIG. 23B provides the −3V VL level, FIG. 23C provides the +5V VHlevel, FIG. 23D provides the −5V VL level, FIG. 23E provides themidpoint +1.5V VR level and FIG. 23F provides midpoint −1.5V VR level.

FIG. 24 illustrates an alternate implementation 2402 for providing theVH, VL and VR levels to analog boundary scan cells in an interposer. Thealternate implementation 2402 comprises digital to analog converters(DAC) and shift and update registers (SUR). The SURs have paralleloutputs coupled to the parallel inputs of the DACs and a serial buscoupled to the TDI, CTL and TDO signals of the 1149.1 TAP. An example ofa shift and update scan cell that could be used in the SUR is shown inFIG. 25. The scan cell responds to CTL input to shift data through ashift bit (S) from TDI and TDO and update the data from the shift bit(S) to the update bit (U) to be output to the DAC on the OUT signal.Multiple FIG. 25 scan cells are serially connected to realize the SUR.The 1149.1 serial bus can be operated to shift in and update theparallel outputs of the SURs to the parallel inputs of the DACs, causingthe DACs to output a desired voltage level. In this example, DAC 2404outputs a desired VH level, DAC 2406 outputs a desired VL level and DAC2408 outputs a desired VR level. It is assumed that the DACs havesufficient output drive to where voltage follower amplifiers (A) are notrequired on the outputs of the DACs.

FIG. 26 illustrates an arrangement 2602 of three serially connectedimplementations 2402 providing three groups 2604-2608 of separate VH, VLand VR levels for each of the above mentioned first, second and thirdanalog boundary scan cell groups. The advantage of arrangement 2602 overusing the voltage dividers of FIGS. 23A-23F to provide the three groupsof separate VH, VH and VR levels is that each of the voltage levels canbe uniquely programmed by different values scanned into the SURs. Inparticular, being able to establish a DAC controlled variable VR to thedigitizing comparator 2104 of the analog boundary scan cells is veryuseful. For example, using a fixed mid point VR provided by a voltagedivider as shown in FIGS. 23E and 23F can test that an analog signalinput crosses the mid point voltage, but it can't test the amplitude ofthe upper and lower swings of the analog signal. Using the DACcontrolled variable VR of FIG. 24, the VR can be set to a mid pointvoltage to test that an analog signal transitions through at least themid point voltage, then the VR can be set to a high point voltage totest that the analog signal transitions at least through the high pointvoltage and then the VR can be set to a low point voltage to test thatthe analog signal transitions at least through the low point voltage.Besides the mid point, high point, and low point voltages, any number ofvoltage levels, based on the resolution of the DAC, can be applied tothe VR signal, which can aid in diagnosing analog signaling problems insystems. The variable VR mid, high and low threshold detection approachcan be used to capture a digitized analog signal in a functionallyoperating system via the 1149.1 “Sample” instruction or it can be usedto capture a digitized analog signal when the system is in an off-linetest mode using the 1149.1 “Extest” instruction.

To reduce circuitry overhead, implementation 2402 may be simplified toonly include the SUR and DAC combination 2408 to only provide the VR.The VH and VL levels of implementation 2402 can be provided using thesimple voltage dividers of FIGS. 23A-23D. This would allow using simplefixed VH and VL drive levels in combination with the DAC programmable VRlevel to achieve the low, mid, high and other VR threshold points statedabove.

FIG. 27 illustrates an arrangement 2702 of three serially connected SURand DAC combinations 2408 providing three separately programmable VRlevels 2704-2708 for each of the above mentioned first, second and thirdanalog boundary scan cell groups.

FIG. 28 illustrates a simpler programmable level VR circuit 2802 thatcould be used to provide only the high, mid and low point VR levelsmentioned above. The circuit includes a SUR, three analog switches2804-2808 and a unity gain voltage follower amplifier (A) 2810. If thehigh point level is to be used as the VR, the SUR will be scanned withcontrol to close switch 2804 and open switches 2806 and 2808. If the midpoint level is to be used as the VR, the SUR will be scanned withcontrol to close switch 2806 and open switches 2804 and 2808. If the lowpoint level is to be used as the VR, the SUR will be scanned withcontrol to close switch 2808 and open switches 2804 and 2806. Thissimpler programmable VR circuit 2802 could be used with fixed voltagedivider VH and VL drive levels to further reduce circuitry overhead.Three serially connected programmable VR circuits 2802 could be arrangedas in FIG. 27 to provide the low, mid and high point VR levels for theabove mentioned first, second and third analog boundary scan cellgroups.

FIG. 29 illustrates three devices 2902-2906 connected to a systemsubstrate 2908 via their inputs 318 and outputs 320. Each devicecontains a number of stacked die 1604 and an 1149.1 interposer 1606 asshown in FIG. 17.

FIG. 30 illustrates the stacked die 1604 of devices 2902-2906 connectedto the functional bussing path 3002 of the substrate via their FIN 106and FOUT 108 signals to enable the devices to communicate. The substratehas FIN signals 3004 to allow it to input signals from an externaldevice, such as a keyboard, and FOUT signals 3006 to allow it to outputsignals to an external device, such as a display. In this example, theboundary register 206 of the interposer TAP 204 is set to allow FIN andFOUT signals to flow freely through the interpose 1606, as indicated bythe TAP being in dotted line.

FIG. 31 illustrates the interposer TAPs 204 of devices 2902-2906connected to a serial bussing path 3102 that connects the interposerTAPs to externally accessible 1149.1 TDI, TCK and TMS input signals 212and the 1149.1 TDO output signal 214. When an 1149.1 controller isconnected to the external 1149.1 input and output signals, theinterposer TAPs can be serially accessed to perform test or otheroperations. One of the most important test operations the interposerTAPs perform is the verification that the FIN 106 and FOUT 108 of theeach device 2902-2906 are properly connected together via the substratebussing path 3002. Since the FIN and FOUT interconnects between thestacked die 1604 and interposer 1606 of each device 2902-2906 weretested after they were assembled to form the device, they do not need tobe retested when the devices are mounted on the substrate. Only the FINand FOUT interconnects between interposer and substrate need to betested. This test operation is performed by loading Extest instructionsinto each interposer's TAP instruction register then operating theboundary register of each interposer TAP to test that the FIN and FOUTsignals of the devices are properly connected together via thesubstrate.

As can be seen in FIG. 31, the FIN 106 and FOUT 108 interconnect testbetween each device 2902-2906 is advantageously achieved using only theinterposer TAP boundary register 206 of each device. Thus the FIN andFOUT interconnect test problems mentioned in regard to FIGS. 11 and 15(i.e. the multiple TMS signal problem of FIG. 11 and multiple TAPs inseries problem of FIG. 15) are eliminated by use of the 1149.1interposer 1606 of present disclosure. Further, the use of the analogboundary scan cells of the disclosure in the interposer's boundaryregister to provide interconnect testing of analog FIN and FOUT signalsadds a further improvement over the FIGS. 11 and 15 interconnect testapproach, since the conventional 1149.1 boundary registers of FIGS. 11and 15 only use digital boundary scan cells to perform interconnecttesting of digital FIN and FOUT signals.

While the interposer boundary register 206 has been described up to thispoint comprising boundary scan cells as described in FIGS. 18-22, theinterposer boundary register may include other types of boundary scancells as well.

FIG. 32 illustrates a conventional observe only type digital inputboundary scan cell 3202 that could be used in the interposer boundaryregister. This type of boundary scan cell would be used on highperformance digital signals that cannot tolerate the multiplexer 1804and buffer 1808 delay of the digital input boundary scan cell of FIG.18. As seen, the digital input signal from the substrate passes directlythrough the interposer's signal path connection to be input to the diestack. The digital input boundary scan cell includes a capture and shift(CS) scan cell 3204 as depicted in FIG. 33. When either the Extest orSample instruction is loaded into the TAP's instruction register, the CSscan cell can capture data from the digital signal path connection andshift it out on TDO.

FIG. 34 illustrates an observe only analog input boundary scan cell 3402that could be used in the interposer boundary register. This type ofboundary scan cell would be used on high performance analog signals thatcannot tolerate the switch 2108 and amplifier 2110 delay of the analoginput boundary scan of FIG. 21. As seen, the analog input signal fromthe substrate passes directly through the interposer's signal pathconnection to be input to the die stack. The analog boundary scan cellincludes a capture and shift (CS) scan cell 3204 and a digitizingcomparator 2104 as described in FIG. 21. When either the Extest orSample instruction is loaded into the TAP's instruction register, the CSscan cell can capture digitized data from the analog signal pathconnection and shift it out on TDO.

FIG. 35 illustrates a bidirectional digital boundary scan cell 3502 thatcould be used in the interposer boundary register. This type of boundaryscan cell would be used on functional digital inputs and outputs of thedie stack that are converted to a digital functional input and output(FIO) signal on the substrate. As seen, a direction (DIR) control signalfrom the die stack is coupled to the control input of a tristate buffer3504 and optionally to the substrate via a digital output boundary scancell 1902, a digital FOUT signal from the die stack is coupled to adigital FIO signal of the substrate via a digital output boundary scancell 1902 and buffer 3504, and the digital FIO signal from the substrateis coupled to a digital FIN signal to the die stack via a digital inputboundary scan cell 1802 and buffer 1808.

During functional output mode, the DIR signal from the die stack canenable buffer 3504 to output the digital FOUT signal from the die stackto the digital FIO signal of the substrate.

During functional input mode, the DIR signal from the die stack candisable buffer 3504 to allow the digital FIO signal from the substrateto drive the digital FIN signal to the die stack.

When a Sample instruction is loaded into the interposer's TAPinstruction register, the output boundary scan cell 1902 on the DIRsignal path can be operated to observe the DIR signal output of the diestack, the input boundary scan cell 1802 on the FIN signal path can beoperated to observe the FIO signal of the substrate and the outputboundary scan cell 1902 on the FOUT signal path can be operated toobserve the FOUT signal from the die stack.

When an Extest instruction is loaded into the interposer's TAPinstruction register, the output boundary scan cell 1902 on the DIRsignal path can be operated to observe the DIR signal output of the diestack and control the control input of buffer 3504 and optionally theDIR output to the substrate, the input boundary scan cell 1802 on theFIN signal path can be operated to observe the FIO signal of thesubstrate and control the FIN signal to the die stack and the outputboundary scan cell 1902 on the FOUT signal path can be operated toobserve the FOUT signal from the die stack and control the data outputto the substrate via buffer 3504.

FIG. 36 illustrates a bidirectional analog boundary scan cell 3602 thatcould be used in the interposer boundary register. This type of boundaryscan cell would be used on functional analog inputs and outputs of thedie stack that are converted to an analog functional input and output(FIO) signal on the substrate. As seen, a direction (DIR) control signalfrom the die stack is coupled to the control input of a tristateamplifier 3604 and optionally to the substrate via an analog outputboundary scan cell 2202, an analog FOUT signal from the die stack iscoupled to an analog FIO signal of the substrate via an analog outputboundary scan cell 2202 and amplifier 3604, and the analog FIO signalfrom the substrate is coupled to an analog FIN signal to the die stackvia an analog input boundary scan cell 2102 and amplifier 2110.

During functional output mode, the DIR signal from the die stack canenable amplifier 3604 to output the analog FOUT signal from the diestack to the analog FIO signal of the substrate.

During functional input mode, the DIR signal from the die stack candisable amplifier 3604 to allow the analog FIO signal from the substrateto drive the analog FIN signal to the die stack.

When a Sample instruction is loaded into the interposer's TAPinstruction register, the output boundary scan cell 2202 on the DIRsignal path can be operated to observe the DIR signal output of the diestack, the input boundary scan cell 2102 on the FIN signal path can beoperated to observe the FIO signal of the substrate and the outputboundary scan cell 2202 on the FOUT signal path can be operated toobserve the FOUT signal from the die stack.

When an Extest instruction is loaded into the interposer's TAPinstruction register, the output boundary scan cell 2202 on the DIRsignal path can be operated to observe the DIR signal output of the diestack and control the control input of amplifier 3604 and optionally theDIR output to the substrate, the input boundary scan cell 2102 on theFIN signal path can be operated to observe the FIO signal of thesubstrate and control the FIN signal to the die stack and the outputboundary scan cell 2202 on the FOUT signal path can be operated toobserve the FOUT signal from the die stack and control the data outputto the substrate via amplifier 3604.

FIG. 37 illustrates a digital boundary scan cell 3702 that could be usedin the interposer boundary register. This type of boundary scan cellwould be used on functional digital outputs of the die stack that neededto be tristate-able on the substrate. As seen, an enable (ENA) controlsignal from the die stack is coupled to the control input of a tristatebuffer 3504 via a digital output boundary scan cell 1902 and a digitalFOUT signal from the die stack is coupled to a digital FIO signal of thesubstrate via a digital output boundary scan cell 1902 and buffer 3504.

During functional mode, the ENA signal from the die stack can enablebuffer 3504 to output the digital FOUT signal from the die stack to thedigital FIO signal of the substrate, or disable buffer 3504 fromoutputting the digital FOUT signal to the digital FIO signal of thesubstrate.

When a Sample instruction is loaded into the interposer's TAPinstruction register, the output boundary scan cell 1902 on the ENAsignal path can be operated to observe the ENA signal output of the diestack and the output boundary scan cell 1902 on the FOUT signal path canbe operated to observe the FOUT signal from the die stack.

When an Extest instruction is loaded into the interposer's TAPinstruction register, the output boundary scan cell 1902 on the ENAsignal path can be operated to observe the ENA signal output of the diestack and control the control input of buffer 3504 and the outputboundary scan cell 1902 on the FOUT signal path can be operated toobserve the FOUT signal from the die stack and control the data outputto the substrate via buffer 3504.

FIG. 38 illustrates an analog boundary scan cell 3802 that could be usedin the interposer boundary register. This type of boundary scan cellwould be used on functional analog outputs of the die stack that neededto be tristate-able on the substrate. As seen, an ENA control signalfrom the die stack is coupled to the control input of a tristateamplifier 3604 via a digital output boundary scan cell 1902 and ananalog FOUT signal from the die stack is coupled to an analog FIO signalof the substrate via an analog output boundary scan cell 2202 andamplifier 3604.

During functional mode, the ENA signal from the die stack can enableamplifier 3604 to output the analog FOUT signal from the die stack tothe analog FIO signal of the substrate, or disable amplifier 3604 fromoutputting the analog FOUT signal to the analog FIO signal of thesubstrate.

When a Sample instruction is loaded into the interposer's TAPinstruction register, the output boundary scan cell 1902 on the ENAsignal path can be operated to observe the ENA signal output of the diestack and the output boundary scan cell 2202 on the FOUT signal path canbe operated to observe the FOUT signal from the die stack.

When an Extest instruction is loaded into the interposer's TAPinstruction register, the output boundary scan cell 1902 on the ENAsignal path can be operated to observe the ENA signal output of the diestack and control the control input of amplifier 3604 and the outputboundary scan cell 2202 on the FOUT signal path can be operated toobserve the FOUT signal from the die stack and control the data outputto the substrate via amplifier 3604.

Use of 1149.1 Clamp Instruction

While the disclosure has mentioned use of the 1149.1 Extest and Sampleinstruction, the 1149.1 Clamp instruction can also be used to control aninterposer's boundary register that is composed of the boundary scancells described in regard to FIGS. 18, 19, 21, 22, 35, 36, 37 and 38.The Clamp instruction allows data that has been preloaded (using the1149.1 Preload instruction) into the boundary scan cells to bestatically output from the boundary scan cells while the TAP's singlebit Bypass register is selected for access between the TAP's TDI and TDOsignals. During the Clamp instruction, interposer input boundary scancells of FIGS. 18 and 21 can maintain static inputs to the die stack andoutput boundary scan cells of FIGS. 19 and 22 can maintain staticoutputs to the substrate. The static conditions may include a digital oranalog high level state, a digital or analog low level state or adisabled (tristate) state.

Once a TAP has been included into an interposer for the purpose ofproviding the above described boundary scan test operations, it can beused for other operations as described in FIGS. 39-55 below.

FIG. 39 illustrates a conventional interposer 3902 providing example V+,V− and G busses and FIN and FOUT signal connections between a systemsubstrate 3904 and a die stack 3906. Since the die stack can consume alarge amount of power during functional operation, the V+, V− and Gbusses paths must provide low impedance paths between the systemsubstrate and die stack to reduce the voltage drop across the V+, V− andG bussing paths, which could effect the functional operation of the diestack and the system it operates in. It would be advantageous to be ableto monitor in real time the voltage drop across the V+, V− and G bussingpaths during functional operation of the die stack in the system.Further, it would be advantageous to monitor in real time the functionalactivity of the FIN and FOUT signals in the system.

FIG. 40 illustrates an interposer 4002 of the present disclosurecoupling die stack 3906 to a substrate 4004. As seen, interposer 4002provides the V+, V−, G, FIN and FOUT connection paths of interposer 3902of FIG. 39. Further, and according the disclosure, interposer 4002provides a TAP 204, a shift update register (SUR) 4006 (as described inregard to FIGS. 24 and 25) and an analog switch (ASW) 4008. The SUR 4006is coupled to the TAP 204 as a selectable data register that can beaccessed from TDI to TDO by a TAP instruction to control ASW 4008. Forsimplification the TAPs 1149.1 interface to the substrate is indicatedby line 4028. ASW 4008 receives input from SUR 4006 to select from aplurality of inputs 4026 that can be coupled to at least one (OUT1) 4022or more (OUT2) 4024 outputs. During operation, the ASW can be controlledby the SUR to select a different one or more inputs 4026 and output theone or more inputs to the substrate, via OUT1 or OUT1 and OUT2. The OUT1and OUT2 signals of the substrate can be output to a tester or otherinstrument to examine the signals. The present disclosure providessupport for two types to signal examination, differential signalexamination and single ended signal examination.

During the differential signal examination method, a first signal isoutput on OUT1 and a second signal is output on OUT2. A tester or otherinstrument measures and analyzes the OUT1 and OUT2 signals to determineif they are operating at expected voltage levels. The differentialmethod can be used to monitor the difference in voltage levels betweenany two signals, including the voltage drop (Vd) between the substratecontact points 4010, 4014 and 4018 and the die stack contact points4012, 4016 and 4020 of the interposer, respectively. For example, tomeasure the voltage drop across the V+ bus from contact point 4012 tocontact point 4010, the SUR 4006 can be set to cause the ASW 4008 tooutput the voltage at the die stack V+ contact point 4012 on OUT1 andthe voltage of the substrate V+ contact point 4010 on OUT2. A tester orother instrument connected to the OUT1 and OUT2 signals of the substrate4004 can measure each voltage and determine the voltage drop across theV+ bussing path between the contact points. By knowing the impedance ofthe of the V+ bussing path, which can be measured when the interposer istested prior to assembly, the current flowing to the die stack via theV+ bussing path can also be determined. Continuous real timemeasurements of the voltage drop across the V+ bussing path can be usedto characterize/trace the V+ power consumption of the die stack duringits functional operation. It can also be used to detect low V+ supplyvoltage levels at the die stack which may cause improper operation ofthe die stack. The voltage drop across the V− bussing path from contactpoints 4016 and 4014 and the voltage drop across the G bussing path fromcontact points 4020 and 4018 can be similarly accessed for continuousreal time measurement of the voltage drops across each path for theabove mentioned reasons.

During the single end signal examination method, a signal is output onOUT1. The OUT2 signal is not required (as indicated by dotted line) ifonly single ended examination method is used. A tester or otherinstrument measures and analyzes the OUT1 signal to determine if it isoperating at expected voltage levels. The single ended examinationmethod can be used to monitor the difference in voltage levels betweenany two signals, including the voltage drop (Vd) between the substratecontact points 4010, 4014 and 4018 and the die stack contact points4012, 4016 and 4020 of the interposer, respectively. For example, tomeasure the voltage drop across the V+ bus from contact point 4012 tocontact point 4010, the SUR 4006 can set the ASW 4008 to output thevoltage at the die stack V+ contact point 4012 on OUT1 for measurementby a tester or other instrument, then the SUR is set to cause the ASW tooutput the voltage at the substrate V+ contact point 4010 on OUT1 formeasurement by the tester or other instrument. The tester or otherinstrument analyzes the voltages at the two contact points and todetermine the voltage drop across the V+ bussing path. Since the singleended voltage drop examination method requires two steps separated intime, it cannot perform the continuous real time voltage dropmeasurement provided by the differential examination method describedabove. The voltage drop across the V− bussing path from contact points4016 and 4014 and the voltage drop across the G bussing path fromcontact points 4020 and 4018 can be similarly accessed using the singleended examination method described above.

In addition to using the SUR and ASW to measure voltages as describedabove, the SUR and ASW can be used to monitor, in real time, thefunctional activity of signals on the interposer's FIN and FOUTconnections 4030. Real time single ended monitoring allows one FIN orFOUT signal to be selected and output on the OUT1 signal. Real timedifferential monitoring allows two FIN or FOUT signals to be selectedand output on the OUT1 and OUT2 signals. A tester or other instrumentconnected to the OUT1 or OUT1 and OUT2 signals can monitor or trace thefunctional operation of the selected signal(s).

FIG. 41 illustrates three devices each including the stacked die 3906and interpose 4002 of FIG. 40 mounted on a substrate 4108. The substrateprovides OUT1 and OUT2 signal paths that are connected to the OUT1 andOUT2 signals of each devices interposer 4002. The substrate providesexternal access of the OUT1 and OUT2 bussing paths to a tester or otherinstrument. The purpose of this illustration is to simply show thatsince the OUT1 and OUT2 signals of the interposers are commonlyconnected on the OUT1 and OUT2 signal paths, only one interposer can beenabled at a time to output its OUT1 and OUT2 signals to the tester orother instrument. When one interposer is selected for outputting itsOUT1 and OUT2 signals, the other interposers are disabled fromoutputting their OUT1 and OUT2 signals.

FIG. 42 illustrates an example differential SUR and ASW circuit 4202.The circuit 4202 includes first and second SUR 4006 sections and firstand second ASW sections 4008. The first SUR section controls the openingand closing of discrete switches in the first ASW section and the secondSUR section controls the opening and closing of discrete switches in thesecond ASW section. The discrete switches have unique inputs (IN-1through IN-N+M) that can be connected to a bus or signal path in theinterposer, commonly connected outputs and a control input from the SUR.The commonly connected outputs are input to a tristate unity gainvoltage follower amplifier (A) 4204 or 4206. Amplifier 4204 of the firstASW section receives control input from the first SUR to enable ordisable the amplifier's output. Amplifier 4206 of the second ASW sectionreceives control input from the second SUR to enable of disable theamplifier's output. When amplifier 4204 is enabled it outputs theselected input (IN-1 through IN-N) on the OUT1 output of the interposer.When amplifier 4206 is enabled it outputs the selected input (IN-N+1through IN-N+M) on the OUT2 output of the interposer. The use oftristate amplifiers 4204 and 4206 allows the OUT1 and OUT2 signals ofinterposers to be commonly connected to the substrate's OUT1 and OUT2signal paths respectively, as described in FIG. 41.

FIG. 43 is provided to illustrate that a single ended SUR and ASWcircuit 4202 only includes the first SUR section 4006 and first ASWsection 4008 of the differential circuit 4202 of FIG. 41.

FIG. 44 illustrates a device 4402 comprising the interposer 1606 of thepresent disclosure and two stacked die 4404 and 4406 that include a TAP204. The TAP 204 of the interposer can be accessed via the 1149.1 inputs212 and 1149.1 output 214 of the interposer as previously described.However the TAPs in die 4404 and 4406 cannot be accessed by the 1149.1inputs 212 and 1149.1 output 214 of the interposer. Thus test, debug andother capabilities that may be provided in the TAPs of die 4404 and 4406cannot be accessed using the interposer of the present disclosure asdescribed up to this point.

FIG. 45 illustrates a device 4502 comprising an interposer 4504 of thepresent disclosure and two stacked die 4504 and 4506 that include a TAP204. While two stacked die with TAPs are shown any number may bestacked. Also only a single die may exist on the interposer.

The interposer 4504 is the same as interposer 1606 of FIG. 44 with thefollowing exceptions. (1) A multiplexer 4510 has been added tointerposer 4504. The multiplexer has an input for receiving a first TDOsignal from interposer TAP 204, an input for receiving a second TDOsignal from the TAP 204 of die 4508 via a TSV path 4516 in die 4506, acontrol input from the IRO output of interposer TAP 204 and an outputcoupled to the TDO output of the interposer.

(2) A gating circuit 4512 has been added to interposer 4504. Gatingcircuit 4512 has an input for receiving the TCK input of the interposer,an input for receiving an enable signal from the IRO output of theinterposer TAP 204 and an output coupled to the TCK input of the TAPs ofdie 4506 and 4508 via TSV path 4518 in die 4506. (3) The TDO of theinterposer TAP is coupled to the TDI input of the TAP of die 4506 via asignal path 4520 between the interposer and die 4506. (4) The TRST inputof the interposer, if implemented, or the output of the POR circuit 316of the interposer 204 is coupled to the TRST inputs of the TAPs of die4506 and 4508 via TSV path 4522. Note, if the die 4506 and 4508 havetheir own POR circuit, this TRST connection between the interposer anddie TAPs may not be necessary. (5) Optionally, a gating circuit 4514,such as shown in FIG. 47, may be added to interposer 4504 in place of orin combination with gating circuit 4512. Gating circuit 4514, if added,has an input for receiving the TMS input of the interposer, an input forreceiving an enable signal from the IRO output of the interposer TAP 204and an output coupled to the TMS input of the TAPs of die 4506 and 4508via TSV path 4524.

In response to a TRST input or a POR signal, the TAPs of the interposer,die 4506 and die 4508 will be reset to the Test Logic Reset state ofFIG. 3A and the instruction register of the TAPs will be set to eitherthe Bypass instruction or to the optional IDCode instruction if it isimplemented. During either of these instructions, the IRO output of theinterposer TAP will set the control input to multiplexer 4510 to selectthe interposer TAP's TDO to be coupled to the interposer's TDO output214. Also the enable input to gating circuit 4512 will be set to gateoff the TCK input of the TAPs of die 4506 and 4508. If implemented, theenable input to gating circuit 4514 will be set to gate off the TMSinput of the TAPs of die 4506 and 4508.

Following reset, the die TAPs are disabled from access and theinterposer TAP is enabled for access. The TAP of interposer 4504 can beaccessed by the interposer's 1149.1 input and output signals exactly asthe TAP of interposer 1606 has been described being accessed. Indeed,following reset, the operations of interposer 4504 and interposer 1606are identical.

When it is desired to access the TAPs of die 4506 and 4508, a die stackaccess instruction is shifted into and updated from the TAP instructionregister of interposer 4504. The die stack access instruction will setthe enable signal on the TAP's IRO output to allow TCK to pass throughgating circuit 4512 to the TCK input of the TAPs of die 4506 and 4508.If implemented the enable signal will allow TMS to pass through gatingcircuit 4514 to the TMS input of the TAPs of die 4506 and 4508. The diestack access instruction will also set the control signal to multiplexer4510 to couple the TDO output of the TAP of die 4508 to the TDO outputof interposer 4504. In response to the die stack access instruction, theinterposer TAP, die 4506 TAP and die 4508 TAP are all serially connectedbetween the interposer TDI and TDO signals and all respond to the TCKand TMS signals to perform data register scan and instruction registerscan operations from TDI to TDO. To maintain the serial TAP accessarrangement, any further die stack access instruction loaded into theinstruction register of the interposer TAP must keep the enable andcontrol signals from IRO outputs set such that the die TAPs receive TCKand TMS signals and the TDO of the TAP of die 4508 is coupled to the TDOoutput of the interposer.

When access to the die TAP has been completed, a non-die stack accessinstruction is scanned into the interposer TAP that sets the enable andcontrol signals of the IRO output to states that disable the TCK and/orTMS signals to the die TAPs and cause the TDO output of the interposerTAP to be coupled to the TDO output of the interposer. In response toany further non-die stack access instruction loaded into the interposerTAP instruction register, data will pass only through the interposer TAPfrom TDI to TDO.

It is important to note that while the interposer 4504 is shownproviding access to two stacked die with TAPs, it can similarly provideaccess to any number of stacked die with TAPs by serially connecting theTAPs of the stacked die in series the TAP of the interposer.

It is also important to note that a die stack may include a die with aTAP and a die without a TAP. In this case the die with the TAP may beserially connected to the interposer TAP as shown in FIG. 45A.

FIG. 46 illustrates an example implementation of gating circuit 4512which comprises a And gate and a flip flop (FF). The TCK signal is inputto an input of the And gate and to the inverted clock input of the FF.The enable (ENA) signal from the interposer TAP IRO output is input tothe data input of the FF and the data output of the FF is input to theother input of the And gate. The output of the FF is the ON/OFF Gatesignal enables the And gate to pass the TCK signal to its output ordisables And gate from passing the TCK signal to its output. The outputof the And gate is connected to the TCK inputs of the die TAPs. Whilenot shown in FIG. 45, the FF receives a reset input from either the TRSTsignal, the POR circuit 316 or from a TAP reset output when the TAP isin the Test Logic Reset (TLR) state of FIG. 3A.

FIG. 47 illustrates the operation sequences of gating circuit 4512 thatinclude a gate “ON” sequence 4702 that enables the TCK to the TAPs ofthe stacked die, an access sequence 4704 where the TAPs of the stackeddie are access from the interposer's TDI and TDO and a gate “OFF”sequence 4706. that disables the TCK to the TAPs of the stacked dieafter access is complete.

In gate “ON” sequence 4702, a die stack access instruction is shiftedinto and updated from the instruction register of the interposer TAP.The update operation occurs after the falling TCK edge 4708 in theUpdate-IR (UIR) state 4716 of FIG. 3A. As seen the ENA signal of theupdated IRO bus goes high shortly after falling TCK edge 4708. From theUIR state 4716, the interposer TAP transitions to the Run Test/Idle(RTI) state 4718 of FIG. 3A on rising TCK edge 4710. The ENA signal isclocked into the FF on the falling TCK edge 4712 of RTI state 4718,which changes the gate output of the FF from OFF to ON. The interposerTAP remains in the RTI state 4720 for at least one additional TCKperiod. The die TAPs start receiving TCKs 4714 during the one additionalTCK in the second RTI state 4720. If the die TAPs were in RTI stateprior to their TCK being enabled, they will remain in the RTI stateduring this one additional TCK period in RTI state 4720. If the die TAPswere in the Test Logic Reset (TLR) state of FIG. 3A, they willtransition to the RTI state to synchronize themselves with the RTI stateof the interposer TAP during this one additional TCK period in RTI state4720. From RTI state 4720 the interposer TAP and die TAPs can transitiontogether from the RTI states to other states of FIG. 3A to performinstruction and data scan access operations, as shown in access sequence4704.

After access to the stacked die is complete, a non-die accessinstruction is shifted in the instruction register of the interpose TAPand updated on the falling edge 4722 the UIR state 4724, which sets theENA signal of the IRO bus low. From the UIR state 4724 the interposerand die TAPs transition to the RTI state 4730. On the falling edge 4728of RTI state 4730 the FF inputs the ENA signal which changes the FF gateoutput from “ON” to “OFF”. When the gate output is “OFF” no further TCKsare input to the die TAPs, forcing them to be idle in the RTI state4730. From RTI state 4730 the interposer TAP alone can continue tooperate through next states (NXS) of the state diagram of FIG. 3A.During subsequent die stack accesses sequences, the die TAPs will starttheir access from RTI state 4730.

Leaving the die TAPs in the RTI state when they are disconnected fromthe interposer TAP is advantageous since information they contain beforebeing disconnected, i.e. instruction and data information, is maintainedwhile they are in the RTI state. For example, the information may beinformation that enables test, debug or monitoring operations in the diewhile they are disconnected from the interposer TAP. The next time theyare connected to the interposer TAP the retained information and theresults of any associated test, debug or monitoring operations areimmediately available to be accessed via the 1149.1 inputs and outputsignals of the interposer.

If no further access to the stacked die is required, it may beadvantageous to move the die TAPs from the RTI state to the Test LogicReset (TLR) state of FIG. 3A to force the die TAPs into a forced resetstate during functional operation of the die stack.

FIG. 48 illustrates a timing sequence 4800 that can be used to connectdie TAPs that have been disconnected in the RTI state to the interposerTAP, then move them from the RTI state to the TLR state. As seen, a diestack access instruction shifted into the instruction register of theinterposer TAP and updated in UIR state 4716 as described in the gate“ON” sequence 4702. The interposer TAP is then transitioned to the RTIstate for a first 4718 and second time 4720 time to enable TCKs to thedie TAPs. The interposer TAP and the enabled die TAPs then transitionthrough the Select-DR (SDR) state 4802 of FIG. 3A, the Select-IR (SIR)state of FIG. 3A to enter the TLR state 4806 of FIG. 3A. The instructionand other circuits of the interposer and die TAPs are reset to safe andknown states on the falling TCK edge of the TLR state 4806. As seen, inTLR state 4806, the interposer TAP outputs a reset signal to the FF ofgating circuit 4512 on the falling TCK edge to set the gate output ofthe FF to the “OFF” state, which gates off the TCK input to the dieTAPs. With the TCK off, the die TAPs remain in the TLR state 4808,regardless of whether the interposer TAP remains in the TLR state ortransitions from the TLR state to other states of FIG. 3A.

If optional gating circuit 4514 of FIG. 45 is used to gate on and offthe TMS signal to the TAPs of the die stack, a suitable circuit can bedesigned to allow gating circuit 4514 to control the TMS signal toprovide the above described “ON” 4702, Access 4704 and “OFF” 4706sequences of FIG. 47 and the “ON” and TLR state entry sequence of FIG.48.

FIG. 49 illustrates an interposer 4504 of a device 4902 being used toserially connect the interposer TAP boundary register with the TAPboundary registers of two stacked die 4904 and 4906. In this arrangementthe 1149.1 input 212 and output 214 bus, illustrated simply as TDI andTDO, of the substrate can be operated to load Extest instructions intothe interposer TAP. Once the Extest instructions are loaded the 1149.1bus can be operated to control the boundary registers to performinterconnect testing between the FIN and FOUT signals 4910 between die4904 and 4906, between the FIN and FOUT signals 4912 between die 4904and the interposer 4504, between the FIN and FOUT signals 4914 betweendie 4906 and the interposer 4504 and between the FIN and FOUT signals4916 and between the interposer 4504 and substrate 4908. Again whileonly two stacked die are shown, any number may exist in the stack.

FIG. 50 illustrates an interposer 4504 of a device 5002 being used toserially connect the interposer TAP with TAPs of die 5004 and 5006. Inthis arrangement the 1149.1 input 212 and output 214 bus, illustratedsimply as TDI and TDO, of substrate 5008 can be operated to allow accessof the TAP of die 5004 that controls Debug circuitry in die 5004. Duringaccess of the Debug circuit TAP of die 5004, the TAPs of the interposerand die 5006 may advantageously be loaded with the Bypass instruction toshorten the TDI to TDO data path length through the interposer and die5006 to only a single bit each.

FIG. 51 illustrates an interposer 4504 of a device 5102 being used toserially connect the interposer TAP with TAPs of die 5104 and 5106. Inthis arrangement the 1149.1 input 212 and output 214 bus, illustratedsimply as TDI and TDO, of substrate 5108 can be operated to allow accessof the TAP of die 5004 that controls Trace circuitry in die 5104. Duringaccess of the Trace circuit TAP of die 5104, the TAPs of the interposerand die 5106 may advantageously be loaded with the Bypass instruction toshorten the TDI to TDO data path length through the interposer and die5106 to only a single bit each.

FIG. 52 illustrates an interposer 4504 of a device 5202 being used toserially connect the interposer TAP with TAPs of die 5204 and 5206. Inthis arrangement the 1149.1 input 212 and output 214 bus, illustratedsimply as TDI and TDO, of substrate 5208 can be operated to allow accessof the TAP of die 5204 that controls Instrumentation circuitry in die5204. During access of the Instrumentation circuit TAP of die 5204, theTAPs of the interposer and die 5206 may advantageously be loaded withthe Bypass instruction to shorten the TDI to TDO data path lengththrough the interposer and die 5206 to only a single bit each.

FIG. 53 illustrates the use of an 1149.1 interposer 1606 or 4504 with astack of die 5304-5306 that are connected to the interposer via bondwires. The interposer 1606 or 4504 operates as previously described totest the interconnectivity between the FIN and FOUT signals of the diestack and a substrate. The interposer can also access TAPs within thestacked die as previously described in regard to interposer 4504.

FIG. 54 illustrates a group of stacked or single die 5404-5406 locatedon an 1149.1 interposer 1606 or 4504. The interposer 1606 or 4504operates as previously described to test the interconnectivity betweenthe FIN and FOUT signal of the group of stacked or single die stack anda substrate. The interposer can also access TAPs within the group ofstacked or single die as previously described in regard to interposer4504.

FIG. 55A-55E illustrates a simplified view of the arrangement of FIG. 54showing only the 1149.1 bussing path and the TAPs 204 of the interposer4504 and stacked or single die 5404-5408. A multiplexer 5502 in theinterposer 4504 allows for selecting different TAP combinations usinginterposer TAP instructions as described in multiplexer 4510 FIG. 45-52.The only difference between multiplexer 4510 and multiplexer 5502 isthat multiplexer 5502 has more inputs for selecting the TDO fromdifferent the TAPs to be output on the interposer TDO.

In FIG. 55A, an instruction is loaded into the interposers TAP tocontrol multiplexer 5502 to allow data to be scanned through theinterposer's TAP via the interposer's 1149.1 input 212 and output 214signals.

In FIG. 55B, an instruction is loaded into the interposers TAP tocontrol multiplexer 5502 to allow data to be scanned through theinterposer's TAP and die 5404 TAP via the interposer's 1149.1 input 212and output 214 signals.

In FIG. 55C, an instruction is loaded into the interposers TAP tocontrol multiplexer 5502 to allow data to be scanned through theinterposer's TAP and die 5406 TAP via the interposer's 1149.1 input 212and output 214 signals.

In FIG. 55D, an instruction is loaded into the interposers TAP tocontrol multiplexer 5502 to allow data to be scanned through theinterposer's TAP and die 5408 TAP via the interposer's 1149.1 input 212and output 214 signals.

In FIG. 55E, an instruction is loaded into the interposers TAP tocontrol multiplexer 5502 to allow data to be scanned through theinterposer's TAP and the TAPs of die 5404-5408 via the interposer's1149.1 input 212 and output 214 signals.

Although the disclosure has been described in detail, it should beunderstood that various changes, substitutions and alterations may bemade without departing from the spirit and scope of the disclosure asdefined by the appended claims.

What is claimed is:
 1. An analog input boundary scan cell comprising:(a) a digital scan cell having a test data input (TDI), a test dataoutput (TDO), a compare input, a first switch output, and a controlinput; (b) a comparator having a voltage reference input, a functionalinput and a compare output coupled to the compare input; (c) a firstanalog switch having a control input coupled to the first switch output,a first voltage input at a first voltage, a second voltage input at asecond voltage different than the first voltage, and a first switchoutput; and (d) a second analog switch having a functional input coupledto the functional input of the comparator, a first switch input coupledto the first switch output, a mode input, and a second switch output. 2.The analog input boundary scan cell of claim 1 in which the digital scancell includes a capture, shift update (CSU) scan cell.
 3. The analoginput boundary scan cell of claim 1 including a unity gain voltagefollower amplifier having an input coupled to the second switch output.4. The analog input boundary scan cell of claim 1 in which thecomparator functional input receives a time varying analog signal. 5.The analog input boundary scan cell of claim 1 in which the firstvoltage is voltage level high and the second voltage is voltage levellow.
 6. The analog input boundary scan cell of claim 1 in which thefirst switch output controls switching the first switch output betweenthe first voltage and the second voltage.
 7. The analog input boundaryscan cell of claim 1 in which the mode input controls switching thesecond switch output between the first switch output and the functionalinput.
 8. An analog input boundary scan cell comprising: (a) afunctional input; (b) a functional output selectively coupled to thefunctional input; (c) a voltage reference input; (d) a test data input;(e) a test data output coupled to the test data input, the functionalinput, and the voltage reference input; (f) a control input selectivelycoupling the test data input to the test data output and selectivelycoupling a combination of the functional input and the voltage referenceinput to the test data output; (g) a first voltage input at a firstvoltage selectively coupled to the functional output; (h) a secondvoltage input at a second voltage different than the first voltageselectively coupled to the functional output; and (i) a mode inputselectively coupling the functional input to the functional output andselectively coupling one of the first voltage input and the secondvoltage input to the functional output.
 9. The analog input boundaryscan cell of claim 8 including a digital scan cell having an inputcoupled to the functional input.
 10. The analog input boundary scan cellof claim 8 including a digital scan cell having an output coupled to thefunctional output.
 11. The analog input boundary scan cell of claim 8including a digital scan cell and a switch coupling the first and secondvoltage inputs to the functional output.
 12. The analog input boundaryscan cell of claim 8 in which the digital scan cell is coupled to thetest data input, the test data input, and the control input.